/*
 * Copyright (c) 1999, 2003, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
 */

package javax.sound.sampled;

/**
 * The <code>LineEvent</code> class encapsulates information that a line
 * sends its listeners whenever the line opens, closes, starts, or stops.
 * Each of these four state changes is represented by a corresponding
 * type of event.  A listener receives the event as a parameter to its
 * {@link LineListener#update update} method.  By querying the event,
 * the listener can learn the type of event, the line responsible for
 * the event, and how much data the line had processed when the event occurred.
 *
 * <p>Although this class implements Serializable, attempts to
 * serialize a <code>LineEvent</code> object will fail.
 *
 * @author Kara Kytle
 * @serial exclude
 * @see Line
 * @see LineListener#update
 * @since 1.3
 */
public class LineEvent extends java.util.EventObject {

  // INSTANCE VARIABLES

  /**
   * The kind of line event (<code>OPEN</code>, <code>CLOSE</code>,
   * <code>START</code>, or <code>STOP</code>).
   *
   * @serial
   * @see #getType
   */
  private final Type type;

  /**
   * The media position when the event occurred, expressed in sample frames.
   * Note that this field is only relevant to certain events generated by
   * data lines, such as <code>START</code> and <code>STOP</code>.  For
   * events generated by lines that do not count sample frames, and for any
   * other events for which this value is not known, the position value
   * should be {@link AudioSystem#NOT_SPECIFIED}.
   *
   * @serial
   * @see #getFramePosition
   */
  private final long position;


  /**
   * Constructs a new event of the specified type, originating from the specified line.
   *
   * @param line the source of this event
   * @param type the event type (<code>OPEN</code>, <code>CLOSE</code>, <code>START</code>, or
   * <code>STOP</code>)
   * @param position the number of sample frames that the line had already processed when the event
   * occurred, or {@link AudioSystem#NOT_SPECIFIED}
   * @throws IllegalArgumentException if <code>line</code> is <code>null</code>.
   */
  public LineEvent(Line line, Type type, long position) {

    super(line);
    this.type = type;
    this.position = position;
  }

  /**
   * Obtains the audio line that is the source of this event.
   *
   * @return the line responsible for this event
   */
  public final Line getLine() {

    return (Line) getSource();
  }


  /**
   * Obtains the event's type.
   *
   * @return this event's type ({@link Type#OPEN}, {@link Type#CLOSE}, {@link Type#START}, or {@link
   * Type#STOP})
   */
  public final Type getType() {

    return type;
  }

  /**
   * Obtains the position in the line's audio data when the event occurred, expressed in sample
   * frames. For example, if a source line had already played back 14 sample frames at the time it
   * was paused, the pause event would report the line's position as 14.  The next frame to be
   * processed would be frame number 14 using zero-based numbering, or 15 using one-based numbering.
   * <p> Note that this field is relevant only to certain events generated by data lines, such as
   * <code>START</code> and <code>STOP</code>.  For events generated by lines that do not count
   * sample frames, and for any other events for which this value is not known, the position value
   * should be {@link AudioSystem#NOT_SPECIFIED}.
   *
   * @return the line's position as a sample frame number
   */
    /*
     * $$kk: 04.20.99: note to myself: should make sure our implementation is consistent with this.
     * which is a reasonable definition....
     */
  public final long getFramePosition() {

    return position;
  }

  /**
   * Obtains a string representation of the event.  The contents of the string may vary
   * between implementations of Java Sound.
   *
   * @return a string describing the event.
   */
  public String toString() {
    String sType = "";
    if (type != null) {
      sType = type.toString() + " ";
    }
    String sLine;
    if (getLine() == null) {
      sLine = "null";
    } else {
      sLine = getLine().toString();
    }
    return new String(sType + "event from line " + sLine);
  }


  /**
   * The LineEvent.Type inner class identifies what kind of event occurred on a line.
   * Static instances are provided for the common types (OPEN, CLOSE, START, and STOP).
   *
   * @see LineEvent#getType()
   */
  public static class Type {


    /**
     * Type name.
     */
    // $$kk: 03.25.99: why can't this be final??
    private /*final*/ String name;

    /**
     * Constructs a new event type.
     *
     * @param name name of the type
     */
    protected Type(String name) {
      this.name = name;
    }

    //$$fb 2002-11-26: fix for 4695001: SPEC: description of equals() method contains typo

    /**
     * Indicates whether the specified object is equal to this event type,
     * returning <code>true</code> if the objects are identical.
     *
     * @param obj the reference object with which to compare
     * @return <code>true</code> if this event type is the same as <code>obj</code>;
     * <code>false</code> otherwise
     */
    public final boolean equals(Object obj) {
      return super.equals(obj);
    }


    /**
     * Finalizes the hashcode method.
     */
    public final int hashCode() {
      return super.hashCode();
    }


    /**
     * Returns the type name as the string representation.
     */
    public String toString() {
      return name;
    }

    // LINE EVENT TYPE DEFINES

    /**
     * A type of event that is sent when a line opens, reserving system
     * resources for itself.
     *
     * @see #CLOSE
     * @see Line#open
     */
    public static final Type OPEN = new Type("Open");


    /**
     * A type of event that is sent when a line closes, freeing the system
     * resources it had obtained when it was opened.
     *
     * @see #OPEN
     * @see Line#close
     */
    public static final Type CLOSE = new Type("Close");


    /**
     * A type of event that is sent when a line begins to engage in active
     * input or output of audio data in response to a
     * {@link DataLine#start start} request.
     *
     * @see #STOP
     * @see DataLine#start
     */
    public static final Type START = new Type("Start");


    /**
     * A type of event that is sent when a line ceases active input or output
     * of audio data in response to a {@link DataLine#stop stop} request,
     * or because the end of media has been reached.
     *
     * @see #START
     * @see DataLine#stop
     */
    public static final Type STOP = new Type("Stop");

    /**
     * A type of event that is sent when a line ceases to engage in active
     * input or output of audio data because the end of media has been reached.
     */
        /*
         * ISSUE: we may want to get rid of this.  Is JavaSound
         * responsible for reporting this??
         *
         * [If it's decided to keep this API, the docs will need to be updated to include mention
         * of EOM events elsewhere.]
         */
    //public static final Type EOM  = new Type("EOM");

    /**
     * A type of event that is sent when a line begins to engage in active
     * input or output of audio data.  Examples of when this happens are
     * when a source line begins or resumes writing data to its mixer, and
     * when a target line begins or resumes reading data from its mixer.
     * @see #STOP
     * @see SourceDataLine#write
     * @see TargetDataLine#read
     * @see DataLine#start
     */
    //public static final Type ACTIVE       = new Type("ACTIVE");

    /**
     * A type of event that is sent when a line ceases active input or output
     * of audio data.
     * @see #START
     * @see DataLine#stop
     */
    //public static final Type INACTIVE     = new Type("INACTIVE");

  } // class Type

} // class LineEvent
